Solid-liquid classification is a process widely utilized in water and wastewater treatment, in chemical industries, mining industries, and any industry utilizing or involving a process step in which materials suspended in a liquid medium must be separated from that liquid medium.
Exemplary of the types of apparatus employed are liquid cyclones which are commonly used for separating sand and other relatively high specific gravity material from water. Grit chambers have also long been utilized in the water and wastewater treatment fields for the separation of sand, and other readily settleable materials, from floatable materials which tend to remain suspended in the water medium. Mechanical centrifuges are also widely applied to solid-liquid mixtures for separating solid fractions from the liquid and producing a dense solid cake or slurry. Free vortex separators have been demonstrated to be extremely efficient devices for concentrating immiscible oils from water. In all these devices, advantage is taken of the specific gravity difference between the material to be removed, or classified, from that of the suspending liquid.
For additional background information reference may be had to Perry's Chemical Engineer's Handbook, 4th Edition, 1963 McGraw-Hill, or to other engineering texts on water and wastewater treatment or mass transfer unit processes.